Qemu network issue

internal error: firewalld is set to use the nftables backend, but the required firewalld ‘libvirt’ zone is missing. Either set the firewalld backend to ‘iptables’, or ensure that firewalld has a ‘libvirt’ zone by upgrading firewalld to a version supporting rule priorities (0.7.0+) and/or rebuilding libvirt with --with-firewalld-zone

Try this:

sudo pacman -S iptables-nft

It will ask you to replace nftables. Then reboot and check if it’s fixed.